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Trivia question- 12G 1316 Head rocker arms
- Thread starter lbcfan
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Hap Waldrop
Yoda
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Yep, the manual is wrong, most 1275s, as Gerard staed came with the stamped steel rocker arms, only the very first ones had the forged units, and they work just fine, they were two varieties of the stamped units and both work fine, the ones with the Vandervell markings on them, than the ones with the PATD stamped into them, they claim these have a tick more lift.
FWIW, the sintered rocker arms came on the later A+ plus Mini engines.
FWIW, the sintered rocker arms came on the later A+ plus Mini engines.
Spridget64SC
Jedi Trainee
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In my builds of LPHP engines, I've been measuring the rocker ratios of the various configurations of rockers (forged and stamped). After a few hundred rockers, I've come up with the Cooper 'S' style forged rockers varying from a nominal 1.23 to 1.25 to 1. The stamped steel versions vary from 1.25 to 1.33 to 1. With the stamped steel variety, there are the narrow rocker pads and the wide rocker pads. The wide pad stamped rockers are used exclusively on 1275s due to the valve spacing. There are "rogue" rockers which fall completely outside of these bands. This is most often due to something being different about the pad curvature or the location of the adjuster screw.
Remember that these engines are no less than 37 years gone from original production and you never know what you will find on the outside or the inside. With the interchangeability of many of the basic engine components, one might find 948cc type forged rockers on a 1275 12V tagged engine. One never knows what a PO might have done to the engine.
HTH,
Mike Miller
Remember that these engines are no less than 37 years gone from original production and you never know what you will find on the outside or the inside. With the interchangeability of many of the basic engine components, one might find 948cc type forged rockers on a 1275 12V tagged engine. One never knows what a PO might have done to the engine.
HTH,
Mike Miller
Thanks! I bought the engine rebuilt and have been trying to place the year. I thought the rocker type might help, and I was curious about the discrepancy. The seller has no idea of the year, but as I said earlier, the block and head numbers seem to place it in 1968-69. I'll let it go at that.
Regards,
Michael
Regards,
Michael
Hap Waldrop
Yoda
Offline
lbcfan said:
All US 1275s had the smog port 12G1316 cylinder head from say 1968-1974, the ealry 67 blocks had a thin oil pan flange in the block and has no pie shaped hole under the center main saddle in the block, the later blocks all had a thicker oil pan flange and a pie shaped hole under the center main bearing sadlle in the block, FWIW, they all are good parts, while thin flange blocks, 12G940 pre smog cylinder heads and EN40B crankshafts are all coveted parts for the "in the know" Spridget lovers, the alternatives work just fine, even in highly stressed race engines. Mike Miller even hold the EN40B crank in less regard than the EN16T, because he had more than one of them break in his race engines, I was always too much of salesman
to keep a EN40B crank for myslef, I always saw them as a way to fund my projects 